If you change the name of the nntp server there is really no way to resume unless you manually rename to control file to match the new newsgroup name.

As far as automatic deletion, I don't think it's useful. Most people who use NNTP gateway with FUD use it to provide both a web interface to a newsgroup as well as a searcheable newsgroup archive. If you must delete you can use the admprune control panel and with minimum effort (remove the admin authentication) you can make it into a cronable PHP script.